In the related art, a cylindrical insulation bobbin of a vehicle alternator has been proposed, in which a slit is provided in a tongue piece which extends in a direction from a base of a rotor core claw section to a claw tip and in which a rib is formed on a claw tip extension section such that local stress due to torsion produced at the time of assembly is dispersed, a crack, damage, or the like to the tongue piece is prevented, and assembling workability is improved (for example, see PTL 1).
Further, a rotor has been proposed, in which a root of a flange section of which a thickness is reduced to be about half the side wall section that forms an accommodation section of a field coil in a part of a bobbin which is similar to PTL 1 is configured to be an S-shaped bent section and high assembling properties and high work efficiency are achieved (for example, see PTL 2).